Wearable protective denim fabrics

ABSTRACT

Provided herein are blended fibers for use in protective clothing which confer protection against electrical arcs and/or flash fire hazards and also have a pleasing appearance, while also being comfortable to wear. The fabrics described herein can be processed to give an aesthetically desired appearance such as a washed denim look.

FIELD OF INVENTION

This disclosure is related to wearable protection fabrics which confer protection against, inter alia, electrical arcs and/or flash fires.

BACKGROUND OF THE INVENTION

Fabrics and garments comprising flame resistant fibers of low tensile strength when exposed to the intense thermal stress of an electrical arc can break open exposing the wearer to additional injury as a result of the incident energy. Electrical arcs typically involve thousands of volts and thousands of amperes of electrical current. The electrical arc is much more intense than incident energy such as from a flash fire. To offer protection against electrical arcs to a wearer of a garment or fabric, the garment of fabric must resist the transfer of energy through the fabric or garment to the wearer. It is believed that this occurs both by the fabric absorbing a portion of the incident energy and by the fabric resisting break open. During break open a hole forms in the fabric directly exposing the surface or wearer to the incident energy.

Currently cotton or cotton/Nylon 66 fabric treated with flame retardant solutions is commercially available, but the treated cotton fabric loses its flame retardant properties as it undergoes different type of washes typically used in production of denim, such as enzyme wash, bleach wash etc. As the flame retardant chemicals are placed on the surface of the treated cotton fabric through in-situ polymerisation of Proban Tetrakis (hydroxymethyl)-phosphonium chloride (THPX) or chemical bonding with cellulose (Pyrovatex), any rupture of the cellulosic cotton fiber causes a reduction in the flame retardant properties.

Flame retardant denim prepared from Meta aramid with flame retardant viscose and Modacrylic blend is currently known. However this fabric only gives a rigid denim look while an after wash look is desirable.

There are also other known denim fabrics in which the warp yarn is cotton or blended with hydrophobic fiber and in the weft, a flame retardant fiber blend is used. However, such fabrics only provide arc protection, not the desirable NFPA 2112 protection because the fabrics do not meet the vertical char length requirement.

The National Fire Protection Association (NFPA) 2112 standard delineates minimum requirements for the design, construction, evaluation, and certification of flame-resistant garments for use by industrial personnel, with the intent of not contributing to the burn injury of the wearer, providing a degree of protection to the wearer, and reducing the severity of burn injuries resulting from short-duration thermal exposures or accidental exposure to flash fires.

There is a need for wearable flame retardant denim which meets functional criteria such as NFPA 2112 criteria and also provides electrical arc protection, while also meeting aesthetic requirements for appearance such as a post-washed look.

SUMMARY OF THE INVENTION

Provided herein are blended fibers for use in protective clothing which confer protection against electrical arcs and/or flash fire hazards and also have a pleasing appearance, while also being comfortable (e.g., breathable) to wear. The fabrics described herein can be processed to give an aesthetically desired appearance such as a washed denim look, while also complying with, inter alia, NFPA 2112 standards.

In one aspect, provided herein is a flame retardant denim fabric comprising

-   -   a blended weft yarn comprising about 45% to about 60% by weight         of a hydrophobic fiber; about 30% to about 50% by weight of a         hydrophilic fiber; and about 5% to about 10% by weight of nylon         66, based on total weight of the blend;     -   a blended warp yarn comprising about 35% to about 25% by weight         of a hydrophobic fiber, and about 65% to about 75% by weight of         a hydrophilic fiber based on total weight of the blend;

wherein the said flame retardant denim fabric confers protection against electrical arcs, flash fire hazards, or both, and is breathable.

In some embodiments of the flame retardant denim fabric, the hydrophobic fiber is modacrylic and the hydrophilic fiber is a cellulosic fiber.

In another aspect, provided herein is a flame retardant denim fabric comprising

-   -   a blended weft yarn comprising about 45% to about 60% by weight         of modacrylic; about 30% to about 50% by weight of cotton; and         about 5% to about 10% by weight of nylon 66, based on total         weight of the blend;     -   a blended warp yarn comprising about 65% to about 75% by weight         of cotton and about 35% to about 25% by weight of modacrylic,         based on total weight of the blend;

wherein the said flame retardant denim fabric confers protection against electrical arcs, flash fire hazards, or both, and is breathable.

In some embodiments of the fabric described herein, a portion of the blended weft yarn further comprises an anti-static filament twisted with the blended weft yarn. In some of such embodiments of the fabric described herein, the blended weft yarn comprises a first blended yarn comprising about 45% to about 60% by weight of modacrylic; about 30% to about 50% by weight of cotton; and about 5% to about 10% by weight of nylon 66, based on total weight of the blend; and a second blended weft yarn comprising about 45% to about 60% by weight of modacrylic; about 30% to about 50% by weight of cotton; about 5% to about 10% by weight of nylon 66, based on total weight of the blend, and further comprising an anti-static filament twisted with the second blended yarn.

In some embodiments of the fabric described herein, the antistatic filament count in the second blended yarn is about 35 to about 45 dtex. In some embodiments of the fabric described herein, the anti-static filament in the fabric is at a regular interval of 8 to 10 mm in the weft direction resulting in about 2.54 to about 3 antistatic filaments per inch in the weft direction.

In some embodiments of the fabric described herein, the spun yarn count is between about 8-20 Ne.

In some embodiments of the fabric described herein, the fabric is finished with softeners; anti-microbial finishing agents, water proofing agents, oil or water repellents, or stain release agents, or a combination thereof.

In some embodiments of the fabric described herein, the fabric has a washed denim look.

In another aspect provided herein is a process for manufacturing the fabric described herein comprising

i) preparing blends for the warp and weft yarns;

ii) spinning yarns from the blends;

iii) twisting antistatic fiber with at least a portion of the weft yarn;

(iv) dyeing and sizing the spun yarns of steps (ii) and (iii);

(v) weaving the fabric with a denim weave in an air jet loom;

(vi) desizing the fabric;

(vii) sanforising the fabric; and

(v) finishing the fabric.

DETAILED DESCRIPTION OF THE INVENTION

All materials used herein were commercially purchased as described herein or prepared from commercially purchased materials as described herein.

Described herein are light weight flame retardant, electrical arc and flash fire protecting yarns/fabrics/garments comprising several aesthetic properties of denim. The flame resistance properties are retained even after different types of denim washes such as enzyme wash, stone wash, oxidation, tint wash and the like. The yarns or fabrics, and garments thereof described herein also comprise antistatic properties and are breathable (air permeable, moisture/vapor permeable) which helps reduce perspiration thereby providing greater comfort to the user for longer periods of time.

Provided herein are yarns, fabrics and garments which, when exposed to the intense thermal stress of an electrical arc resist the transfer of energy, reduce energy transfer by absorbing a portion of the incident energy and, through charring, allow a reduction in energy transmitted to the wearer of said garments and/or garments prepared from said yarns and fabrics. Further, the yarns, fabrics and/or garments described herein are cotton based and are also flame resistant.

Cellulosic fibers such as cotton, although softer and less expensive than inherently flame retardant fibers, are not naturally resistant to flames. To increase the flame retarding capability of these fibers, one or more flame retardants are incorporated into or with the cellulosic fibers (e.g., by spinning the flame retardant into the cellulosic fiber, coating the cellulosic fiber with the flame retardant, contacting the cellulosic fiber with the flame retardant and allowing the cellulosic fiber to absorb the flame retardant, or any other process that incorporates a flame retardant into or with a cellulosic fiber).

In one aspect, provided herein are yarns or fabrics, and/or garments thereof, comprising modacrylic with cotton blend in the warp yarn and modacrylic with cotton and nylon 66 blend in the weft yarn. Accordingly, the fire retardant polymer modacrylic is blended in both the weft and the warp yarn. In one group of embodiments, yarns or fabrics, and/or garments thereof, further comprise one or more antistatic strips, thereby allowing for improved protection against electrical arcs.

In weaving, the weft refers to the thread or yarn which is drawn through, or inserted over-and-under, the lengthwise warp yarns that are held in tension on a frame or loom to create cloth. In other words, warp is the lengthwise or longitudinal thread in a roll of cloth, while weft is the transverse thread.

The fiber/polymer blends described herein confer wearable protection without compromising aesthetic properties like colour, breathability, durability etc. The combination of hydrophobic fiber (Modacrylic and nylon 66) and hydrophilic fiber (cotton) allows for establishment of moisture management in the fabric due to increase in capillary force resulting in high wicking properties of the yarn and/or fabric, and/or garments thereof. The presence of modacrylic confers flame retardant properties; and surprisingly, there is no impact of different denim washes on the flame retardant properties of the fabric.

In one group of embodiments, provided herein is a fabric wherein the warp yarn comprises about 65% to about 75% by weight of cotton and about 35% to about 25% by weight of modacrylic, based on total weight of the fabric. By way of example only, an embodiment of the fabric described herein comprises a warp yarn having 70% cotton/30% modacrylic, which yarn is dyed through ring dyeing method. In another group of embodiments, provided herein is a fabric wherein the weft yarn comprises about 45% to about 60% by weight of modacrylic; about 30% to about 50% by weight of cotton; and about 5% to about 10% by weight of nylon 66, based on total weight of the fabric. By way of example only, an embodiment of the fabric described herein comprises a weft yarn having 50% modacrylic/45% cotton/5% nylon 66 with an antistatic strip which is capable of dissipating static charge.

In one embodiment, the fabrics described herein comprise two weft spun yarns. The first weft spun yarn comprises a blend of modacrylic, cotton, and Nylon 66. The second weft spun yarn comprises the same blend used for the said first weft spun yarn and further comprises an antistatic filament twisted with it. In one group of embodiments, the spun yarn count is between about 8-about 20 Ne, where the unit Ne refers to the number of 840 yards (hanks of cotton) in one pound of fibers, yarns and/or thread. In one group of embodiments, the antistatic filament count in the second weft spun yarn is about 35 to about 45 dtex, or about 39 dtex, where decitex (abbreviated dtex) is the mass of fibers, yarns and/or thread in grams per 10,000 meters.

The flame retardant properties of the blended-yarn-woven fabrics described herein are retained throughout the life of the garment including the processing steps and the washings by the wearer of the garment. The fabric is more absorbent because of enhanced capillary forces in the fiber blends while also providing all the aesthetic properties of denim.

By “yarn” is meant an assemblage of fibers spun or twisted together to form a continuous strand, which can be used in weaving, knitting, braiding, or plaiting, or otherwise made into a textile material or fabric.

“Antistatic Strip” means anti-static filament at a regular interval in the weft direction. By way of example, anti-static filament is twisted with the weft yarn such that it occurs at a regular interval of 8 to 10 mm in the weft direction approximating to about 2.54 to about 3 antistatic filaments per inch in the weft direction.

“Modacrylic fiber” refers to acrylic synthetic fiber made from a polymer comprising primarily acrylonitrile. Preferably the polymer is a copolymer comprising 30 to 70 weight percent of an acrylonitrile and 70 to 30 weight percent of a halogen-containing vinyl monomer. The halogen-containing vinyl monomer is at least one monomer selected, for example, from vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide, and the like. Examples of copolymerizable vinyl monomers are acrylic acid, methacrylic acid, salts or esters of such acids, acrylamide, methylacrylamide, vinyl acetate, etc.

“Redox potential” means the measure of the tendency of a chemical species to acquire electrons and thereby be reduced. Redox potential is measured in volts (V), or millivolts (mV).

The fabrics described herein are not treated with a flame retardant post weaving; rather, the fabrics described herein are woven from blended yarns obtained from blending of cotton and flame retardant polymers as described herein. Thus the fabrics provided herein have high tensile and tear strength, high abrasion resistance, and high dimensional stability compared to fabrics prepared by other methods. The yarns/fabrics/garment described herein comprise cotton/polymer blends which confer moisture management traits to the garment (e.g., breathable fabric/garment so that the garment stays dry on the wearer despite perspiration). As a part of the finishing process for the fabric, functional finishes like softeners (e.g., non silicon base softeners such aspolyethylene, polyurethane), anti-microbial finish(e.g., quaternary ammonium, metallic salts of Ag, Zn,Cu and the like, Triclosan(2,4,4-hydrophenyl trichloro (II) ether), Chitosan and the like), water proofing(e.g., fluorocarbon coating, polyurethane coating or lamination), oil/water repellence(e.g., fluorocarbon finish), stain release (e.g., fluorocarbon finish) etc. are applied on the fabric described herein without affecting thermal/electrical arc protection properties.

The fabrics described herein are useful in manufacture of protective garments, especially garments that have use in industrial applications where workers may be exposed to electrical arcs or flash fires. The garments include and are not limited to coats, coveralls, jackets, shirts, pants, sleeves, aprons, and other types of apparel where protection against fire, flame, and heat is needed. The denim-based protective wear described herein meets compliance standards of NFPA 2112, ISO 11611. ISO 11612, ASTM F1959/F1959M-13, and/or ISO 61482-1-1. EN 1149.

EXAMPLES

Spinning:

In one example, yarn is made from 8 Ne to 20 Ne, with the parameters listed below:

Twist Multiplier: 4.0 in single yarn.

Blend for Warp:

Cotton: 65% to 75% by weight of the total blend

Modacrylic: 35% to 25% by weight of the total blend

Blend for Weft 1:

Modacrylic: 45% to 60% by weight of the total blend

Nylon 66: 5% to 10% by weight of the total blend

Cotton: 30% to 50% by weight of the total blend

Blend for Weft 2:

With the same blend of first weft spun yarn is twisted with 39 dtex antistatic filament.

The Modacrylic, cotton, Nylon 66 fiber are spun in a ring spinning system.

Process sequence:

BLOW ROOM-CARD-TWO DRAW FRAME PASS—SPEED FRAME-RING FRAME-WINDING

Blow Room: Opening and blending of the different fibers in specific proportion is carried out prior to sending to next machine by chute feed system.

Carding: Card machine cleaning of all the impurities, naps etc. to obtain output sliver.

Draw frame: drafting and making fibers more parallel and removing hooks.

Speed frame: To obtain roving which is the input material of ring frame.

Ring frame: To make single yarn.

Winding: to make bigger package.

Warping: Making warp sheet for dyeing.

Dyeing and Sizing:

The dyeing and sizing is carried out by a process sequence in a slasher dyeing machine or rope dyeing machine. The sequence of dyeing in a slasher dyeing machine is as follows:

Prewetting-Washing-Dyeing bath-Washing-Horizontal drying range-Sizing-Horizontal drying range-Accumulator-Dry split-Winding

Prewetting: First bath—remove natural and added impurities by treating the yarn sheet with NaOH, sequestering agent and wetting agent at 60° C. for 10 Sec to improve the dyeability.

Washing: Second and Third Bath—Washing with water at 60° C. to remove impurities.

Dyeing Bath: Fourth to ninth Bath—Indigo dyestuff as per shade, NaOH, Sodium Hydrosulphite, sequestering agent and wetting agent taken to maintain redox potential (−660 mV to −680 mV), pH 11.3 to 11.6.

Contact time in each bath is about 10 Sec with aeration time of 40 Sec between two baths. Aeration is required for dyes to air oxidize.

With the above parameters the yarn sheet (warp sheet) is dyed.

Washing: Tenth to Twelfth Bath—To remove the excess colour, three bath washing is conducted at an initial bath temperature of 60° C. and two more washes at 40° C. Contact time in each bath is 10 seconds.

Horizontal drying range (HDR): After dyeing, the warp sheet is dried in a HDR to 9 to 10% moisture.

Sizing: Then the warp sheet goes to a size bath which contains starch, lubricant, antistatic agents etc. at a temperature of 90° C. Sizing enhances the weavibility properties such as lubrication, binding, strength and antistatic properties.

Horizontal drying range (HDR): To dry the warp sheet up to a point where residual moisture is about 9% to about 10% of the initial moisture content.

Accumulator: To accumulate yarn.

Dry split: To separate out individual yarns.

Winding: To make weaver's beam.

Weaving:

Fabric is made in air jet loom with any denim weave comprising 3/1 twill, 2/1 Twill, 4/1 twill or derivatives of twill weave. In this example, 3/1 Twill Weave was used with predefined parameters for loom ends per inch (epi) and picks per inch (ppi).

The weight range of denim fabric is about 280 gsm-about 450 gsm.

For example for 350 gsm warp 12s Ne, weft 1: 8s Ne, Weft 2: 8s Ne +39 dtex antistatic.

With on loom epi: 72 and PPI: 48

Anti-static filament as weft yarn is inserted at a regular interval of 8 to 10 mm in weft direction i.e. the 2.54 to 3 antistatic filament per inch in weft direction.

Desizing:

In this process singeing, desizing and washing is done. First the fabric goes through a gas burner with an intensity of about 8 to about 10 mbar, to burn the protruding fibers which improves the pilling tendency and lustre. Than the fabric padded with enzyme, sequestering agent and wetting agent at 80° C. After a suitable reaction time the fabric goes to a steamer. With this sequence the size i.e. starch is converted to soluble dextrin. After a washing treatment in a 4-box counter current water flow system to remove soluble dextrin, the fabric goes to a Vertical Drying Range for drying.

Finishing: The fabric is given a soft hand feel by hydrophilic softener on a stenter machine.

Other durable features like anti-microbial coating, water and oil repellants, stain release agents etc. are also incorporated at this stage of the process.

Sanforising: The fabric is allowed to shrink in length as well as width direction to provide a permanent dimension.

Garmenting: After sanforising the fabric, it is now ready for garment making with flame retardant trims.

The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and nature of the invention. 

1. A flame retardant denim fabric comprising a blended weft yarn comprising about 45% to about 60% by weight of a hydrophobic fiber; about 30% to about 50% by weight of a hydrophilic fiber; and about 5% to about 10% by weight of nylon 66, based on total weight of the blend; a blended warp yarn comprising about 35% to about 25% by weight of a hydrophobic fiber, and about 65% to about 75% by weight of a hydrophilic fiber based on total weight of the blend; wherein the said flame retardant denim fabric confers protection against electrical arcs, flash fire hazards, or both, and is breathable.
 2. The flame retardant denim fabric of claim 1, wherein the hydrophobic fiber is modacrylic and the hydrophilic fiber is a cellulosic fiber.
 3. The flame retardant denim fabric of claim 1, wherein a portion of the blended weft yarn further comprises an anti-static filament twisted with the blended weft yarn.
 4. The flame retardant denim fabric of claim 1, wherein the blended weft yarn comprises a first blended yarn comprising about 45% to about 60% by weight of modacrylic; about 30% to about 50% by weight of cotton; and about 5% to about 10% by weight of nylon 66, based on total weight of the blend; and a second blended weft yarn comprising about 45% to about 60% by weight of modacrylic; about 30% to about 50% by weight of cotton; about 5% to about 10% by weight of nylon 66, based on total weight of the blend, and further comprising an anti-static filament twisted with the second blended yarn.
 5. The flame retardant denim fabric of claim 4, wherein the antistatic filament count in the second blended yarn is about 35 to about 45 dtex.
 6. The flame retardant denim fabric of claim 4, wherein the anti-static filament in the flame retardant denim fabric is at a regular interval of 8 to 10 mm in the weft direction resulting in about 2.54 to about 3 antistatic filaments per inch in the weft direction.
 7. The flame retardant denim fabric of claim 1, wherein the spun yarn count is between about 8-20 Ne.
 8. The flame retardant denim fabric of claim 1, wherein the flame retardant denim fabric is finished with softeners, anti-microbial finishing agents, water proofing agents, oil or water repellents, or stain release agents, or a combination thereof.
 9. A flame retardant denim fabric comprising a blended weft yarn comprising about 45% to about 60% by weight of modacrylic; about 30% to about 50% by weight of cotton; and about 5% to about 10% by weight of nylon 66, based on total weight of the blend; a blended warp yarn comprising about 65% to about 75% by weight of cotton and about 35% to about 25% by weight of modacrylic, based on total weight of the blend; wherein the said flame retardant denim fabric confers protection against electrical arcs, flash fire hazards, or both, and is breathable.
 10. The flame retardant denim fabric of claim 9, wherein a portion of the blended weft yarn further comprises an anti-static filament twisted with the blended weft yarn.
 11. The flame retardant denim fabric of claim 9, wherein the blended weft yarn comprises a first blended yarn comprising about 45% to about 60% by weight of modacrylic; about 30% to about 50% by weight of cotton; and about 5% to about 10% by weight of nylon 66, based on total weight of the blend; and a second blended weft yarn comprising about 45% to about 60% by weight of modacrylic; about 30% to about 50% by weight of cotton; about 5% to about 10% by weight of nylon 66, based on total weight of the blend, and further comprising an anti-static filament twisted with the second blended yarn.
 12. The flame retardant denim fabric of claim 11, wherein the antistatic filament count in the second blended yarn is about 35 to about 45 dtex.
 13. The flame retardant denim fabric of claim 11, wherein the anti-static filament in the flame retardant denim fabric is at a regular interval of 8 to 10 mm in the weft direction resulting in about 2.54 to about 3 antistatic filaments per inch in the weft direction.
 14. The flame retardant denim fabric of claim 9, wherein the spun yarn count is between about 8-20 Ne.
 15. The flame retardant denim fabric of claim 9, wherein the flame retardant denim fabric is finished with_softeners, anti-microbial finishing agents, water proofing agents, oil or water repellents, or stain release agents, or a combination thereof.
 16. A process for manufacturing a denim fabric comprising i) preparing blends for the warp and weft yarns; ii) spinning yarns from the blends; iii) twisting antistatic fiber with at least a portion of the weft yarn; (iv) dyeing and sizing the spun yarns of steps (ii) and (iii); (v) weaving the fabric with a denim weave in an air jet loom; (vi) desizing the denim fabric; (vii) sanforising the denim fabric; and (v) finishing the denim fabric. 